There have been efforts of adding hot-plug capability to computer servers. Since in general it is difficult to ascertain the hot-plug requirement and usage of each server at the time of design, adding hot-plug hardware to each PCIe slot in the system (e.g., 4-8 slots per server) is costly even though only one or two slots will be occupied. Most servers do not run with any plugin card. A plugin card may also have a different form factor than the one a server provides. For example, a server may only provide half height Peripheral Component Interconnect (PCI) Express (PCIe) slots hence incapable of handling full height PCIe cards.
Usually one or more PCIe switches are deployed in a computer chassis. Since a conventional PCIe fabric only allows a single root complex, each chassis can only be connected to one server. In order to upgrade (e.g., from one PCIe generation to another generation) to new PCIe switches, all components within the chassis (e.g., a motherboard and/or card hosting the PCIe switch and slot, a management processor) need to be replaced. This is mostly due to all the components are tested and bound to the PCIe switch. Such a configuration is not flexible and cost inefficient.